Sextant



H. A. HUGHES AND T. Y. BAKER.

SEXTANT.

APPLICATION FILED APII.27. i920.

Batented July 5, 1921-.

2 SHEETS-SHEET l H. A. HUGHES AND T. Y. BAKER.

sExTANr.

APPLICATION FILED APR2T| 1920. L. Patented July 5, 1921.

2 SHEETS-SHEET 2.

f designed to reduce the size of the'instrumcnt ENRY Annxiiivnnit ii'UeirEs'Qor Lorrnoiv; ANDiiiioi/IAS YiioMANs BAKiin; on

n sLoUGn, ENGLAND.

isaeso'.

To all whom it may concern: 1 Beiit -known that we, HENRY-ALEXANDER HUGHES, of 59 Fenchurch street, in the city and county voi: London, England, and THOMAS YnoMANs BAKER, of Admiralty Com ass Observatory, Slough, in the county uCkingham, England, Yhave invented new, and ,useful improvements in'Sextants, of which the following is a specification.

vThis invention relates to sextants and con.- sists-in an improved mode of construction while retaining the usualV range of'movement and reducing .the cost of manufacture.--

According to the present invention'the limb of the instrument is in the form .of a segmenti of acircle whereon the telescope is mounted while the index mirror-is fixed to a carrier which isi attached to 4theyperiphery oisaid limb and is adjustable thereonnfor reading the angle subtended` the object Aunder observation. j drawing is illustrative The accompanying of a sextant constructed vaccording tol this invention, 1 y i Figure 1- being in side elevationand Y v Fig. 2 a view of .thefront e'ndi Fig. 3 is a sectional view on the line 3-3 in Fig. l.

Fig. 4 is a sectional view on the line lf-4 in Fig. 3,

Fig. 5 is a sectional view. on the line 5-5 in Fig. l, and n f Fig. 6 is a diagram showing the operation of the device.

In the construction illustrated the limb a of the instrument is in the form of a segment of a circle and has mounted thereon the telescope b.

This telescope is by preference attached to the limb L at two points'b b2 at one of which (b) it is pivoted while at the othei` point (b2) the telescope is capable of angular adjustment by means of a clamping screw b3 working through a slot b4 in av which is mounted on the limb a and which serves as the horizon mirror.

The index mirror d is mounted upon a carrier e ormed or provided with an in- 'Specication of Letters Patent.

Application filed April 27, 1920. Serial No. 377,065.

`a leaf spring g.

a view of; the instrument;V

Patented July 5,

wardly extending flange le khaving a V- shaped recessV e2 'which fits on to a correspondingly shapedV projection formed upon a flange a provided along the periphery of the limb a. yThe under side ofqthis lflange is concave and is formed withrinclinedV groovesto'rreceive a screwV thread formed upon a spindle f. The inner end of this spindley is 'recessed vto receive a supporting pin f projecting from a block f2 pivotally '65 ymounted upon a pin f3 carried ina yoke v epro'vided at the'right handendroil the lower side of the carriage e. The spindle fand the block f2 are inclosed in a casing gf which on the left hand end is provided with The end ofthis spring]vv bears against; the under side of aV yoke le f provided at vthe left'fhand end of theV lower side of the carrier e. The yoke etfstraddles vthe casing .g 'andis provided withfa fixed ,ingerpiece g2 and withy athumb piece l -which is pivotedV upon the'v inger piece and" 1 is pressed by a spring g4 so that normally Athe thumb piece presses the casingfgv and overcomes the pressurelof the spring g.

In this 'manner the screwthreaded end of the spindle f is held in engagement with the 1i underside of the r-flange a? of the limb.'A Dis-.wz

engagement for quick adjustment is effected by pressing the thumb piece g3 thus relieving .the pressure of the spring g4 with the result that the spring g moves the casing g together with the spindle f about the pivot f3, and disengages the spindle f from the flange a.

The carrier e may now be moved directly by hand for adjusting the position of the index mirror. For nal adjustment the outer end of the spindle f is provided with a head f4 whereby the spindle is turned to adjust the carrier e together with the mirror d along the flange a.

rl`he prism c is housed in a casing c pivotally mounted upon the limb w and said casing is provided eccentrically with a pin c2 which engages in a groove 7b formed at one end of an adjusting screw It. This screw works in a casing 7b2 mounted at the back of the limb a and by advancing or withdrawing the screw in its casing the prism c is moved about its pivot for the purpose of adjustment.

Fivotally mounted upon the casing o are the tinted glasses o3 usually employed as shades.

The carrier e on which the index mirror 0l 1 flange e? of the'limb'a, Y A v Y lFori holding the, instrument thelilnbc .is providedfwith a handle arnountefd on .the side;

tending from theV inner edge of the lirnb and at a right angle thereto.

correspondingly shaped projection :on the thereof.

Y degrees O fal circle.` alongfthefffiange a@ on which` the :carrier e' of the index mirror iol a Works, said carrier being n iarkedwith :an Y' a I 'roW-head.v for reading the* angular ad'just'ff .ment .of the carrier. vThe spindle TV7' for" :adL g justingthef carrier ehasby preference the`v Y screwthreads thereon edualli'n p it'chto 7 20th .thelange mrforrnsra segment; 25,;

the limb a; To enableV readings to bel Vtaken and by reflection `from the, prism.' The; tele-'- scope is,.adjnsted aboiit itsjpivot bfi. toallow Y- 'ofe-less, than half a degree the-head ot-the :Spindle f is1.div-id ed into y30. Vdivisions: -Which again' mayibesubdivided so that'readings of fninutes land 1 seconds vcan be' taken-from the? j head; fa in conjunction Vwith the. pointer fs `n1onted on .the casin gfg Vv :f ai

Thezteleseope b. 's soarrangedlin'frelationl? to the prisni e thatlight rays enter the-tele'- The guide j?. iS curved and concentric With the Yflange a/"atv 1 l the outerl edge ofthe limb a, The carrier e is f 'f liheld on this `flange Vbythe V-shapedfreces's in the flange e" of the carrierv` engaging with theA In this Amanner Zone revolution of the die n fl moves the carrier half degree along more or less `of` the reflectedjlightithan Athe direct light to Venter thetelescope as desired Inv adj listing the yinstrument the 'carriere "of the 4in'deX mirror Z is set to'fzerofand an ob'- ser'vationtaken by the telescope on the object beneath the prism c; The prism 0 is now ad- Yj usted until animage of the object-isv 'reflected from thern'i'rror d into theprism 'c and thence tothe telescope, two superposedimag'es ofthe object being then seen. The facesofthe inf f i What ` In 's asextant, al-limblin theforml ofi.afsegey i' vdex 'mirror d and the'prisln c Will1no WbeY parallel tof-eachothenlas shown in-fnlllines in.y F ig. 6. To fascertain'theJ-angle snbtendedf. Y Y by'an objectrelativelyto another lower obf j i The -lin'lbw is .marked in degrees vandha'liqjector `thehorizong thefloiv'ver objection-the Y horizonI is iviewed ldirectly-' through, theA tele; scope' b and beneaththef prism e, lThe:index-J. Inifrror'd i s `now adjusted-i iintill"the".Iipp'erVVV -object visI 'eflected.'frorn the mirrori'ntoz the4 Y Y Prism ci and. thencexinto thev vupper portion of the telescope, the anglesubtendedfbeing"A i then read on the scale oft-he sextant.'i-'lfhe position ofthe mirror d showninldottedlinesf;V represents anv angle of 90 to;the iho'r i'z"onfl Y Y Weclairnas our invention and desire 1 -f @to SejCrebY Letters-Patentliseement oan annnlus, acarrier slidablebodily. vi

thereon ,in the arc of acircle Whose centerles ii outsideythefsextant, means for! adj u stinggthe 'Y 1 carrier! on; the' liinb," an index mirror V,onthe 'carrie'r.,V a horizon prism mounted: on sai/ d i, lmba' @11dV .an @616500199 '70D'. .thefflllb-f arranged' Y vrela'tifvfely' to the'l lprismito.reeeiife'direct rays-f Y Y; -j offlight from beneath the prisni and A-retlectech l [rays therefrom; substantially ias described; v 1 Y HENRY- ALEXANDERLHUGHE 

